Water in swimming pools is usually filtered and treated with chemicals to maintain the quality of water within suitable levels and in compliance with local regulations. Filtration systems are designed to eliminate, e.g., suspended solids, including microbial and algal growth, floating debris, and oil and greases in the water. Conventional systems for maintaining water quality in swimming pools typically involve large centralized filtration systems that are expensive to construct and to operate. A conventional centralized filtration system is usually configured to filter the entire volume of water in a pool from about 1 to 6 times per day. The operation of such centralized filtration systems is energy intensive and causes swimming pools to have a large carbon footprint and limits the maximum size of conventional swimming pools.
Water is typically directed to the centralized filtration system from three sources: the main body of water in the pool; water suctioned from the bottom of the pool containing settled impurities; and water drawn from the surface of the pool by skimmers. All three sources are treated by the same centralized filtration system regardless of different levels and types of impurities. In addition, conventional centralized filtration systems operate according to certain defined periods of time, or for certain amount of hours a day without taking into account the real time condition of the water being treated and/or without adjusting operational parameters and filtration requirements to optimize efficiency of the system in view of the real time condition of the water being treated.
Conventional centralized pool filtration systems therefore have high equipment costs and consume large amounts of energy to complete such filtration requirements. The Association of Pool and Spa Professionals estimates that there are more than 5.5 million swimming pools in the United States equipped with conventional centralized filtration systems. According to the U.S. Department of Energy, conventional pool filtration systems are very energy intensive, using up to 3,000 kWh of electricity per year, the equivalent of about 30% of an average household's electricity consumption, as per the Energy Information Administration. The California Energy Commission estimates that a typical backyard swimming pool in California can use enough energy during the summer season as would be needed to power an entire home for three months. Reducing the amount of energy needed for filtration would provide savings in the cost of maintenance of the pools and also reduce CO2 emissions.
The cost and high energy demand of operating a pool with conventional centralized filtration systems has caused closures of some large public swimming pools around the world. For example, according to the Japan Times, the “Ocean Dome” indoor swimming pool located in Japan (which holds the Record Guinness as the largest indoor swimming pool in the world, with over 1 hectare of water surface) had to be closed in 2007 due to high operational costs. Another example is the “Fleishhacker Pool” located in California, with a surface of 1.5 hectares, which had to be closed on 1971 due to water quality problems and high costs.
With a trend toward more sustainable and ecological practices, regulatory agencies throughout the world are enacting regulations that aim to lower energy consumption and reduce CO2 emissions of swimming pool operations. Because of the need for lower energy consumption and more cost effective filtration systems, it is desirable to have a method that is capable of maintaining water quality at a lower capital and operating cost. A trend toward more sustainable operations is also driving the need for more energy efficient systems and methods for maintaining water quality in large water bodies, such as swimming pools.